1. Field
This invention relates to the art of substrates micro-fabrication and, more particularly, to patterning of substrates, e.g., the magnetic layers of a hard disk for hard disk drives.
2. Related Art
Micro-fabrication of substrates is a well know art employed in, for example, fabrication of semiconductors, flat panel displays, light emitting diodes (LED's), hard disks for hard disk drives (HDD), etc. As is well known, fabrication of semiconductors, flat panel displays and LED's involves various steps for patterning the substrate. On the other hand, traditional fabrication of hard disks, generally referred to as longitudinal recording technology, does not involve patterning. Similarly, fabrication of disks for perpendicular recording technology does not involve patterning. Rather uniform layers are deposited and memory cells are generally defined by the alternating change of magnetic flux induced by the recording head, with each recording bit encompassing multiple grains within the un-patterned magnetic layers.
It has been demonstrated that non-patterned disks would fail to satisfy the needs of the market, in terms of area bit density and costs, in order to remain competitive with other forms of storage. Consequently, it has been proposed that next generation disks should be patterned. It is envisioned that the patterning process may utilize photolithography, although currently there is no certainty which lithography technology may be commercialized, and no commercial system is yet available for commercial manufacturing of patterned media. Among contenders for photolithography are interference photolithography, near field lithography and nano-imprint lithography (NIL). Regardless of the lithography technology utilized, once the photoresist is exposed and developed, the disk needs to be etched and fabricated according to the desired pattern. However, although much development efforts have been focused on the patterning step, many obstacles still exist for fabricating a patterned disk in a commercially viable environment.
To be sure, etch, sputtering, and other fabrication technologies are well known and well developed for semiconductor, flat panel display, LED's, etc. However, these technologies need to be integrated together with viable processes to enable commercial fabrication of patterned disks for HDD. Moreover, unlike HDD disks, in all of the other applications only one side of the substrate needs to be etched—allowing a chuck to hold the substrate from the backside during fabrication. On the other hand, HDD disks need to be fabricated on both sides, preventing the use of a chuck. Indeed, in HDD disk fabrication, no part of the fabrication system may contact any surface of the disk. Also, while HDD manufacturers expect the system to have a throughput on the order of 1000 disks per hour, fabricators of semiconductors employ systems having throughputs of only tens of substrates per hour.
Prior art patterning typically consists of steps that are broken down to the processing and/or etching of each layer individually. Typical process sequence include: descum, carbon hard mask opening by ion milling, followed by etching the magnetic layer by ion milling, and followed by mask removal. The above approach, while effective in forming the final etched magnetic feature, is very cumbersome and slow. Typical process time for each step can be a few minutes up to a few tens of minutes, thus rendering these approaches (broken steps with ion milling) impractical for rapid commercial production. The important duty cycle which is critical to the ultimate purpose of the patterned media is not addressed.